Sensors for inductive plethysmographic monitoring applications and apparel using the same

ABSTRACT

This invention includes improved IP sensors that both have improved sensitivity, performance, and other properties and are multifunctional. The improved IP sensors have IP sensor conductors with waveforms having legs that are substantially parallel throughout the operating range of stretch. The multifunctional IP sensors include, in addition to IP sensors, accessory conductors, additional sensors, and other compatible modules. This inventions also includes embodiments of apparel incorporating the improved IP sensors. This apparel can range from band-like to shirt-like, and so forth, and include one or more IP sensors sensitive to expansions and contractions of underlying regions of a monitored subject.

This application is a divisional of U.S. application Ser. No.13/242,929, filed on Sep. 23, 2011, now U.S. Pat. No. 8,777,868, whichis a continuation of U.S. application Ser. No. 11/233,317, filed on Sep.21, 2005, now U.S. Pat. No. 8,024,001, which claims the benefit of U.S.provisional application No. 60/611,900, now expired, filed Sep. 21,2004, and of U.S. provisional application No. 60/699,698, now expired,filed Jul. 15, 2005; each of these applications are incorporated byreference in their entireties herein for all purposes.

FIELD OF THE INVENTION

The present invention provides improved sensors for inductiveplethysmographic (“IP”) monitoring applications and embodiments ofapparel incorporating the improved sensors; in particular the improvedsensors have improved performance and multifunctional capabilities.

BACKGROUND OF THE INVENTION

Inductive plethysmography (IP) is a measurement technology useful forphysiological monitoring, especially for ambulatory physiologicalmonitoring. IP sensors can be disposed on monitored subjects, eitherdirectly or attached to or incorporated into various kinds ofcomfortable, unobtrusive garments, for example, in bands, or inpartial-shirts, or in shirts, or on partial body suits, or in full bodysuits, or in caps, and the like. See, e.g., U.S. Pat. No. 6,551,252 B2issued Apr. 22, 2003. Often, respiration is monitored by combiningsignals from an IP sensor about the rib cage (RC) and an IP sensor aboutthe abdomen (AB). Coefficients used for combining RC and AB signals inrespiration signals can be determined by calibration procedures. See,e.g., U.S. Pat. No. 4,834,109 issued May 30, 1989 and U.S. Pat. No.6,413,225 B1 issued Jul. 2, 2002. It is also known that differentiallung function can be obtained by combining signals from more localizedIP sensors overlying the right and left lungs. See, e.g., U.S. Pat. No.5,159,935 issued Nov. 3, 1992. All four of these cited patent areincorporated herein by reference in their entireties for all purposes.

Further, signals from one or more IP-based sensors about a subject'sthorax and/or abdomen can be processed and interpreted to provide, forexample, respiratory rates, respiratory volumes, and indications ofrespiratory events such as coughs and the like. See, e.g., U.S. patentapplication Ser. No. 10/822,260 filed Apr. 9, 2004 (which isincorporated herein by reference in its entirety for all purposes).Signals from one or more IP-based sensors about a subject's thorax atthe level of the xiphoid process can be processed and interpreted toprovide, for example, cardiac stroke volumes, and the like. See, e.g.,U.S. Pat. No. 6,783,498 B2 issued Aug. 31, 2004 (which is incorporatedherein by reference in its entirety for all purposes).

Generally, an IP sensor includes a conductive element that is placedabout, usually enclosing, a portion of the body to be monitored. As thesize of the enclosed body portion changes, for example, because ofrespirations and/or cardiac contractions, electrical properties of theconductive element changes. Sensor electronics measures these change andproduces output signals, which can be processed into data reflective ofareas, circumferences, diameters, and similar geometric measures, of themonitored body part enclosed body cross section. The resulting area,circumference, diameter, and similar information is useful forphysiological monitoring applications.

Since it is important that the conductive element, usually a wire, movewith the monitored body part, this element is usually not directlymounted but it supported by an elastic material which is in contact withthe monitored body part. The supporting elastic material has usuallybeen a knitted, woven, crocheted, or braided textile on which the sensorwire is mounted and affixed in a wavy, sinuous, or approximatelysinusoidal pattern. See, e.g., U.S. Pat. No. 6,341,504 B1 issued Jan.29, 2002 (which is incorporated herein by reference in its entirety forall purposes).

However, these known IP sensors have generally been limited toperforming only IP sensor functions. Furthermore, their sensor functionshas lacked desirable sensitivity, performance, and other importantsensor properties.

Citation or identification of any reference in this section or anysection of this application shall not be construed that such referenceis available as prior art to the present invention.

SUMMARY OF THE INVENTION

Therefore, objects of this invention include providing improved IPsensors that are both multifunctional and have improved sensitivity,performance, and other properties. Objects of this invention alsoinclude embodiments of apparel incorporating the improved sensors.

This improved sensor includes a supporting elastic material that isintended to be arranged on a body part of the monitored subject. When soarranged, the material is stretchable through an operating range ofstretch by expansion and contraction of the underlying body part. Thematerial includes one or more sensor conductors operably affixed to theelastic material in a pattern of repeated unit waves that stretch andcontract with the supporting elastic material. Each of these the wavesis configured to have leg portions that are substantially parallel andremain substantially parallel throughout the operating range of stretch.Preferably, the leg portions deviate no more than approximately ±2° orless from parallelism throughout the operating range of stretch.

The unit waves of the sensor conductor preferably have a spatialfrequency greater than approximately 5 per in., and more preferablyapproximately 6 per in., when the supporting elastic is stretched atless that the operating range of stretch. The conductors are preferablyof a fine a wire as is consistent with DC resistance requirements, andis usually of 27 AWG or higher. As the sensor conductors stretch andcontract throughout the operating range of stretch, an electricalcharacteristic of the sensor conductor changes, preferably linearly withthe stretch of the supporting. The electrical characteristic is usuallyan AC impedance which preferably is substantially,

The sensor conductors can have various orientations with respect to thesupporting elastic. For example, their leg portions can extendsubstantially perpendicularly to the surfaces of the supporting elastic,or their leg portions can be substantially parallel and remainsubstantially parallel throughout the operating range of stretch, ortheir leg portions can be angled to extend perpendicular between thesurfaces of supporting elastic and parallel along the surfaces of thesupporting elastic.

The sensor of this invention are can include one or more accessoryconductors affixed to the elastic material. Their pattern also comprisesrepeated unit waves that stretch and contract with the supportingelastic material, but the unit waves of the accessory conductor and theunit waves of the sensor conductor usually have different spatialfrequencies and preferably have a smooth pattern without substantiallyparallel leg portions. In particular, the accessory conductor have aspatial frequency preferably less than approximately 3 per in. Theaccessory conductors can include comprises micro-coax. A sensor oftenhas two or more sensor conductors and four of more accessory conductorsand up to ten or more total conductors.

When applied to inductive plethysmography (IP), the sensor conductorsare bridged and are operably linked to conductors external to thesupporting elastic. Thus, when seen from the external conductors, twosensor conductors are electrically continuous. This configuration allowadvantageous arrangements on monitoring garments where the sensorconductors need not be interrupted by garment, lines of closure andlimits external connections to a single location on the sensorconductors.

These sensor can include one or more additional sensors affixed to thesupporting elastic, such as microphones, body-temperature thermometers,ECG electrodes, accelerometers, sensors for electroencephalogramsignals, sensors for electrooculogram signals, sensors forelectromyogram signals, and the like. Such additional sensors areadvantageously operably linked externally by an accessory conductorwhich conveys signal from the sensor.

The elastic material can be woven, and/or knitted, and/or crocheted,and/or braided material, and/or extruded material, of the like.Generally, the materials are made by conventional means and machinesknown in the art but adapted to distribute conductors across thematerials surface.

This invention also includes methods of physiologically monitoring asubject that employ the improves sensors of this invention. Thesemethods include arranging an improved sensor on a body part of themonitored subject, and measuring an electrical characteristic of thesensor conductor which changes as the supporting elastic is stretchedthroughout the operating range of stretch and from which conductorlength can be determined. The electrical characteristic is usuallymeasured across external leads operably linked to the sensor conductors.The measured characteristic is AC impedance that is usuallysubstantially inductive in nature and that varies with substantially nohysteresis throughout the operating range of stretch. The variation withstretch is preferably as rapid as possible, and more preferably linearthroughout a substantial fraction of the operating range.

In preferred embodiments, these characteristics are measured by applyingan excitation signal to the sensor conductor that possess a frequencydetermined at least in part by the sensor conductor. The frequency ofthe excitation signal is then measured.

This invention also includes physiological monitoring apparel thatinclude the improved IP sensors of this invention. The apparel includesa worn by a subject that supports the supporting elastic material andthe IP sensor. The garment can be band-like, or shirt-like, or beotherwise configures

Different physiological information can be obtained by careful placementon sensors on the garment. For example, by arranging one sensorconductor arranged on a left lateral part of the rib cage of the subjectand another sensor conductor on a right lateral part of the rib cage ofthe subject, differential lung function can be determined by comparingdifference between the two rib-cage measurements. Also, total lungfunction can be determined by cumulating both the measurements.Measurement quality can be improved by includes one sensor conductorarranged on a left lateral part of the abdomen of the subject andanother conductor on a right lateral part of the abdomen of the subject,and by combining these abdominal signals with the rib cage signals.

These garments can include additional sensors either attached to the IPsensor supporting elastic or otherwise carried by the garment.Additional sensors can include microphones, body-temperaturethermometers, ECG electrodes, accelerometers, sensors forelectroencephalogram signals, sensors for electrooculogram signals,sensors for electromyogram signals, and the like. The IP sensor usedhere and the garments can also have one or more accessory conductorsthat often link the additional sensor to processing circuitry. Thegarment fabric, as well as the supporting elastic, material, can bewoven, and/or knitted, and/or crocheted, and/or braided, and/or extrudedmaterial, and so forth.

In a preferred embodiment, the invention includes a physiological sensorfor a monitoring a subject that comprises a supporting elastic materialadapted to be arranged on a body part of the monitored subject and, whenso arranged, stretchable through an operating range of stretch byexpansion and contraction of the underlying body part; at least onesensor conductor operably affixed to the elastic material in a patterncomprising repeated unit waves that stretch and contract with thesupporting elastic material wherein each unit wave is configured to haveleg portions that are substantially parallel and that remainsubstantially parallel throughout the operating range of stretch.

Aspect of this preferred embodiment include: that the leg portionsdeviate approximately ±2° or less from parallelism throughout theoperating range of stretch; that, when the sensor is not stretched, theleg portions converge together from crest of a unit wave to the base ofthe unit wave; that the unit waves of the sensor conductor have aspatial frequency greater than approximately 5 per in. when thesupporting elastic is stretched at less than the, operating range ofstretch; that the unit waves of the sensor conductor have a spatialfrequency greater than approximately 6 per in. when the supportingelastic is stretched at less than the operating range of stretch; andthat sensor conductor comprises wire of 27 AWG (America Wire Gauge) orhigher.

Further aspect of this preferred embodiment include: that an electricalcharacteristic of the sensor conductor changes as the supporting elasticis stretched throughout the operating range of stretch; that theelectrical characteristic is substantially free of hysteresis over aplurality of cycles of stretching and relaxation; that the plurality ofcycles of stretching and relaxation comprises a period of monitoring thesubject; that the period of monitoring the subject is less than onehour, or less than twelve hours, or less than twenty-four hours; thatthe electrical characteristic comprises an AC impedance of the sensorconductor; the impedance is substantially an inductive impedance; andthat the electrical characteristic depends substantially linearly on thestretch in a substantial portion of the operating range of stretch.

Further aspect of this preferred, embodiment include: that the IPconductor is affixed to the supporting elastic so that when the IPsensor is arranged on the body part, the electrical characteristic issubstantially free of hysteresis over a plurality of cycles ofstretching and relaxation; that at least one accessory conductor affixedto the elastic material in a pattern comprising repeated unit waves thatstretch and contract with the supporting, elastic material, wherein theunit waves of the accessory conductor have a spatial frequency less thanthe spatial frequency of the unit waves of the sensor conductor; thatthe unit waves of the accessory conductor have a spatial frequency lessthan approximately 3 per in; that the unit waves have a smooth patternwithout substantially parallel leg portions; that the accessoryconductor comprises micro-coax; that the sensor conductors arepositioned between the accessory conductors.

It should be understood that sensor of the preferred embodiment isincluded in additional embodiments of the physiological sensors of thisinvention and of the apparel of this invention. Similarly, the aspectsof this preferred embodiment can be included the above additionalembodiments. Further aspects and details and alternate combinations ofthe elements of this invention will be apparent from the followingdetailed description and are also within the scope of the inventor'sinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be understood more fully by reference to thefollowing detailed description of the preferred embodiment of thepresent invention, illustrative examples of specific embodiments of theinvention and the appended figures in which:

FIG. 1 illustrates an embodiment of processing of IP sensor signals;

FIG. 2 illustrate preferred IP sensor performance;

FIG. 3 illustrates an embodiment of the preferred patterns of IP sensorconductors;

FIG. 4A-C illustrate an implementation of the preferred patterns of IPsensor conductors;

FIGS. 5A-B illustrate other embodiments of the preferred patterns of IPsensor conductors;

FIGS. 6A-C illustrate arrangement of IP sensor conductors in IP sensors;

FIGS. 7A-B illustrate an implementation of the preferred patterns ofaccessory conductors;

FIGS. 8A-C illustrate embodiments of multifunction IP sensors;

FIGS. 9A-C illustrate a garment including IP sensors; and

FIGS. 10A-B illustrate another garment including IP sensors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Following a summary of IP technology, described herein are preferredembodiments of the improved inductive plethysmographic (“IP”) sensorsconfigurations of this invention; then multifunctional and otherwise,improved IP sensors; and finally, novel, and/or exemplary applicationsof these IP sensors and elastic materials in physiological monitoring.In the following (and in the application as a whole), headings andlegends are used for clarity and convenience only.

Inductive plethysmography (IP) provides signals reflecting the varyingsizes of a body part, specifically the volume of the body part. Anelastic IP sensor that include a conductive element is arranged on abody part in a manner so that the conductive element expands andcontracts along with the underlying part. Since the electricalproperties, often the inductance, of the conductive element vary withits physical configuration, measurements of the element characteristicswill reliably reflect size of the body part. Specifically, theelectrical properties vary with the length of the sensor, so that, whena sensor is arranged to substantially enclose a body part, aplethysmographic volume can be derived from the sensor output. In mostcases, instead of directly attaching an IP sensor conductor to themeasured body part, the sensor conductor is operably affixed or operablymounted on an elastic material, e.g., a woven, knitted, braided, or thelike, band, and this elastic material can then be arranged on the bodypart, e.g., by being part of a garment.

As used herein, an “IP sensor” is such a combination of a sensorconductor (or sensor “conductive element”), the “sensor conductor”, andsupporting elastic material, the “supporting elastic”. The IP sensor islinked to “IP electronics”, which measures varying electricalcharacteristics of the sensor conductor and preferably provides adigitized output signal. “Operably affixed” or “operably mounted” isused herein to mean that the conductive element is affixed to thesupporting elastic so that it will change proportionally as thesupporting elastic stretches and contracts. The sensor conductor may beoperably affixed by, e.g., incorporation into the elastic. Althoughthroughout the following description the sensor conductor is describedas a wire of particular characteristics, this is not limiting. In otherembodiments, the sensor conductor can be, e.g., formed from a metallicor non-metallic conductive thread or filament. Also, although throughoutthe following description the supporting elastic is usually a woven,knitted, braided, or the like, band, this also is not limiting.Supporting elastic can be manufactured by other techniques.Additionally, a sensor conductor may be affixed directly to a partiallyor entirely elastic garment which then serves as the supporting elastic.

IP sensor electronics can measure an electrical characteristic of thesensor conductor by the various means known in the arts that areappropriate, e.g., by being suitably miniaturizeable and portable, to aparticular embodiment of this invention. In the preferred IP sensor tobe described, the impedance is primarily inductive and a preferredmeasurement technique indirectly measures inductance by applying anexcitation signal to the sensor element and using the natural resonancefrequency as dictated by the impedance of the sensing element to inferan output value that is linear in relation to the sensor's elongation.This measurement technique, illustrated by FIG. 1, incorporates thesensor conductor into an oscillator circuit in a manner so that theoscillator frequency will vary with inductance of the sensor conductor.Oscillator frequency is then detected, digitized, and output using oneof the known, reliable and accurate frequency detection techniques.

This measurement As illustrated, sensor conductor 11 is connected bylink 13 to impedance measuring circuit 14, impedance being determined byinductance at the frequency of the excitation signal. Sensor conductor11 may be in the form of a circumferentially-continuous loop. Morepreferably as subsequently described, the sensor conductor is arrangedso that it is not circumferentially continuous, but instead isinterrupted in a limited region 12. In preferred embodiments, impedancemeasuring circuit includes oscillator 15, which is configured to matchthe response characteristics of the oscillator circuit with those of thesensor conductor across the operating frequency range of the oscillator.The sensor conductor in cooperation with other elements of theoscillator tuning circuit 17 determines the frequency of oscillatoroutput signal 19. Finally, frequency detector 21 detects oscillatorfrequency by known techniques, such as, e.g., by counting signal cyclesduring a reference time interval; or by phase locking oscillator 15 to astable reference frequency (not illustrated); or the like.

Preferred Arrangement of IP Sensor Conductors

The inventors have discovered preferable IP sensors with considerablyimproved performance the remain within practical constraints such asmanufacturability, cost, and the like. The following describes preferreddesign, principles leading to the improved sensors of this inventiondiscovered and applied by the inventors. The following also describesthe designs of particular improved sensors that are preferred forembodiments of this invention directed to measuring chest and abdomensizes and that can be readily manufactured and activated by miniatureand portable sensor electronics. It should be understood that theseparticular preferred sensors are not limiting, because they representone balance sensor of performance against other important sensorcharacteristics for a few current measurement tasks.

Other balances lead to different preferred embodiments. And in view offollowing description, it will be readily apparent to one of skill inthe art how to make improved sensors that represent different balancesof performance against other characteristics and/or that are suitablefor other measurement tasks. For example, sensor performance can beimproved even further in embodiments where manufacturability is lessimportant. Also, sensors can be developed for measurement of body partsof animals of all sizes. Indeed, animal physiological monitoring,veterinary medicine, or the like, are expected and intended applicationsof this invention. Furthermore, it will also be readily apparent how toadapt current improved sensors to future technologies for conductiveelements, elastic materials, and garments.

With this in mind, FIG. 2 illustrates a transfer characteristic of apreferred IP sensor of the invention. The horizontal axis illustratesthe relative linear elongation, or stretch, of a sensor. Relativestretch is a measure of the ratio of a baseline dimension of an IPsensor to the same dimension when the IP sensor is stretched by, e.g.,expansions and contractions of an underlying body part such as a chestof a measured subject. It is a preferred stretch measure because itapplies equally to IP sensor of a wide range of dimensions. Duringnormal operation, relative stretch generally varies between theillustrated bounds, S_min and S_max, where S_min is the stretch when thebody part being, measured is most contracted while S_max the stretchwhen the body part is more expanded. Overall, relative stretch comparedto minimum sensor dimension is preferably 100% or more. For typicalphysiological measurements, the operating, range of relative stretch isfrom 0.1% or less up to 10-15% or less for most physiological process.Additionally, IP sensors should be at least comfortable and unobtrusiveto a monitored subject for stretch throughout the operational range ofrelative stretch. The modulus of the sensor elastic should be large sothat the sensor conductor has little or no motion with respect to themeasured body part during use, yet not so large as to require astretching force that is obtrusive or uncomfortable to a wearer.

In response to varying stretch, an electrical characteristic of thesensor conductor, usually its AC impedance, also varies in a mannergenerally illustrated by the graphed response line in FIG. 2. Thevertical axis in FIG. 2 illustrates possible values of the sensor'selectrical characteristic, usually impedance. The response (or transfer)characteristic illustrated by an exemplary sigmoidal curve that isusually realized by actual sensors. This exemplary curve is notlimiting; other transfer characteristics are possible and have beenfound. More preferred IP sensor conductors are arranged to have asubstantially linear transfer characteristic throughout as much of theoperating range as possible. Most preferred sensor, have a linearcharacteristic throughout the entire operating range. Deviations fromlinearity of more than ±10% are generally substantial; preferablydeviations are no more than ±1%, or even more preferably no more than±0.1%.

The response characteristic of sensor of this invention has importantpreferred properties. A first important property is that thecharacteristic lacks significant hysteresis. More explicitly, as thesensor stretches 26 and relaxes 26′ the value of the electricalcharacteristic when the sensor is at a particular level of stretch issubstantially identical to values when the sensor was previously at thatparticular level of stretch and will be identical when the sensor willbe at that particular level of stretch. In other words, the transfercharacteristic is as illustrated by line 25; the sensor's electricalcharacteristic is uniquely and precisely defined at each level ofstretch in the operational range of stretch. The accuracy by whichstretch can be inferred from a current electrical characteristic islimited by variability due to hysteresis. If an accuracy of 1% orbetter, or 0.1% or better, or similar, hysteresis must be substantiallyabsent to the extent that variability due to hysteresis is less than 1%or better, or less than 0.1% or better, respectively, and so forth.

Practically, hysteresis is preferably substantially absent within atleast one measurement session. The transfer characteristic preferablydoes not drift overall between measurement sessions. If such driftoccurs, interpretation of sensor output is preferably adjustedaccordingly. Preferred sensor have no or limited drift over a lifetimeof 10, or 20, or 30, or more million cycles of stretching andrelaxation.

Another important characteristic of the sensor conductor configurationis that the slope of the transfer characteristic in the operating rangeof relative stretch be as great as possible. With larger the slopes,relative stretch can be inferred from measured electrical characteristicwith more accuracy. Consequently, the largest slopes within otherconstraints are preferred.

Given a preferred IP sensor with substantially no hysteresis (to thedesired level of accuracy) and as great a slope as possible, thepreferred operating range can be selected as follows. When the sensor issubstantially free of stretch 27 the sensor conductor is generally morelimp and free to move with respect to the elastic or to not stretch withthe elastic. In these stretch ranges, the transfer characteristicbecomes flatter and more non-linear, even unpredictable, S_min should beset above region 27. When the sensor approaches a physical limit ofstretch 29, the sensor conductor is unable to respond equally to furtherincreases of stretch and the transfer characteristic becomes flatteragain. S_max should be set below this region. In FIG. 2, the preferredregion of operation relative stretch is 25.

The electrical characteristic of the preferred IP sensors is ACimpedance. Further, the impedance of the preferred sensor at anoperating frequency range is predominantly inductive. Response slope isimproved as the inductive component of the impedance increases.Resistance and capacitance of the sensor conductor should be minimized,and in preferred sensors R is approximately 0.5Ω and C is approximately30 pF. As seen by the electronics, the linking wires to the sensorelements (13 in FIG. 1) are an electrical part of said element andpreferably contribute a negligible amount of impedance variation whensubjected to positional changes. Practical preferred values for sensorof the length required in adult subjects are less than 1Ω resistance and60 to 100 pF capacitance. The DC resistance of the sensor conductiveelement should be kept to a minimum (preferably, approximately 1Ω orless).

The particular preferred sensors as implemented in this applicationoperate in a frequency range from approximately 150 kHz to approximately600 kHz, and preferably in a frequency range from approximately 300 kHzto approximately 310 kHz. In more physiological application, therelative frequency change across the operational range of stretch willbe small so the associated electronics preferably accurately measuresfrequency, e.g., accuracy of 1 part in at least 8000. Hysteresis shouldbe absent to A similar level.

It should be noted that since the frequency itself is linear with1/SQRT(L), designing to have a strictly linear L would result in anon-linear frequency response. More generally, instead of specific Lvalues, it is preferred to be able to infer from the sensor electricalcharacteristic a value that is linear in relation to stretch. In fact.Thus, response characteristic 25 in FIG. 2 should be as steep aspossible while maintaining the largest possible linear zone when thesensor element varies from unstretched to beyond the upper limit of therange of operational stretch. The linear portion is expected to be seensomeplace in the middle of these two mechanical limits.

Otherwise stated, the preferred IP sensors are a form of length sensor,responding to relative changes in their length. Further, they functionas length sensors in a wide range of sizes and three-dimensionalconfigurations, even if formed into a three dimensional shape. It isbelieved that this is because their inductance is due primarily to localmagnetic fields of nearby unit waves (see below) and only littleaffected to magnetic fields of distant portions of the sensor.

It has been found that the preferred IP sensors described below as wellas sensors constructed according to design guidelines in thisapplication have the above preferred characteristics. The preferredsensors to be described have a range of relative stretch in which ahysteresis free transfer characteristic is found, and moreover in amajority of instances, have a substantial linear region within thatrange of stretch. Given a preferred sensor, therefore, a lower bound andan upper bound on the relative stretch can be found within which thesensor satisfies the preferred sensor characteristics. An operationalrange of relative of relative stretch, that is an S_min and an S_max,can then be selected within this range. In many case, the operationalrange can be selected so have a substantial linear region. A linearregion is considered substantial if it, is at least or greater than onehalf of the operational range of relative stretch.

The preferred transfer characteristic described are achieved with thepreferred arrangements of the sensor conductors on the supportingelastic. A sensor conductor is operably affixed as a waveform ofcomprising repeating substantially similar unit waves. FIG. 3schematically illustrates an IP sensor, e.g., sensor 33 having twosensor wires 37 and 39 mounted on supporting elastic 41 in such apreferred pattern. Indicated also are conventional unit wave parametersamplitude (A) and wavelength (Λ) (wavelength is the inverse of frequency(F), or Λ=1/F) It is preferable that the manufacturing variation on bothA and F be as small as manufacturing constraints permit, and in any caseless than approximately 10%, variations of approximately 20% or more areto be avoided.

For IP sensor wires, the frequency parameter, F, should be as large,again, as manufacturing constraints allow, but not so large that theaffixed conductor limits elasticity to the point of causing problems fora wearer For example, for woven, crocheted, and the like elastic, Fcannot exceed spatial frequency of the elastic's fibers or threads.Further, with increased F, the supporting elastic carries more conductorwhich can impede stretchability and even become sensible or obtrusive toa wearer, even it F is not large enough to interfere with sensorelasticity. In the case of supporting elastic that is woven, crocheted,knitted, or the like, an F of approximately 5.0/in. (inch) or greater ispreferable; an F of approximately 5.5/in. or greater is more preferable.Where the supporting elastic, its manufacture, and the weight of theconductor permits, F's of approximately 6.0/in. or greater are morepreferably. Generally, the amplitude, A, should also be as large aspossible, limited by available space on the supporting elastic and alsoby manufacturing constraints and wearer comfort. A is usually less thanor approximately 1-2 in. In most preferred embodiments, an A ofapproximately 0.5 in or greater has been found satisfactory.

As will be discussed, it is often advantageous to have, instead of onesensor wire of amplitude A, two linked sensor wires in the space wherethe one wire would have been and with amplitude of approximately A/2.Sensor performance of two linked wires with amplitudes A/2 has beenfound to be approximately that of one sensor wire of amplitude A otherthings being equal. FIG. 3 illustrates such an arrangement of twoparallel sensor wires in a space on the supporting elastic. Two linkedsensor wires each with an A of 0.3 in to 0.5 in or greater has beenfound satisfactory. These parameters can be combined as anamplitude-wavelength ratio (or equivalently, a amplitude-frequencyproduct). A value of this product of approximately 1.5 of greater ispreferred, a value of 2 or greater is more preferred. Using an evennumbered sensor conductors wires is also advantageous because then theterminus (external contacts) points of the conductors can be locatedclose to each other. This permits operating the sensor element in anyclosed open or overlapping physical configuration without problems ofinterruption or external connection. Such a configuration also aids inattaining preferred properties for the linking wires (13 in FIG. 1).

Further, the shape of the unit waves has been discovered to be animportant design feature. Generally, preferred unit waves have risingand falling portions (referred to herein as the “legs” of the unitwaves) that are on-average substantially parallel throughout theoperating range of stretch (from S_min to S_max). “Wavy”, or “sinuous”,or “sinusoidal”, or the like, patterns that non-parallel or inclinedlegs are less advantageous and are not part of this invention. Preferredunit waves can have average substantially parallel throughout theoperating range of stretch, these shapes differ primarily in how pairsof adjacent legs are bridged. Bridges (also, referred to herein as“caps”) can vary between more square-like and linear present in more“square-like” unit waves and more rounded and smoothly varying presentin more “U-like” unit waves, with more square-like unit waves beingsomewhat preferred to more U-like waves. Preferred unit waves haveamplitude-wavelength ratios of approximately 2 or greater, with greaterratios being more preferred.

FIG. 3 illustrates an illustrated particular preferred sensor patternhaving more

U-like unit waves at three degrees of stretch. The illustrated unitwaves have substantially parallel legs 45, and adjacent legs are bridgedwith more rounded caps 43. Importantly, the legs remain substantiallyparallel over an operating stretch range, from a stretch below theoperating range 31, to an average operating stretch 33, and to anincreased stretch above the operating range 35. Further, across theoperating range, the wave pattern responds substantially linearly tostretch. For example, at lesser stretch 31, the indicated distancemarkers 47 and 49 mark the length of ten unit waves; at averageoperating stretch, 33, the same markers mark nine unit waves; and atgreater stretch, 33, the same markers mark only eight unit waves.Although the unit waves illustrated in FIG. 3 are preferred and entirelyadequate for the present invention, more square-like unit waves would besomewhat more preferred. The substantially parallel portion of the legsshould extend over at least half of the unit-wave amplitude, andpreferably over two-thirds or more of the, amplitude.

Furthermore, it is apparent that, in the sensor pattern of FIG. 3, legsof the unit waves remain virtually parallel throughout the operatingrange of stretch. In the absence of constraints, such sensor patternsare realizable with precise manufacturing methods. However, because ofmanufacturing constrains, cost constraints, and other constrainingfactors, actual implementations of preferred sensors of this inventionoften have unit waves with legs that, while remaining substantiallyparallel throughout the operating range of stretch, do not remain asparallel as in FIG. 3. Somewhat constrained implementations with sensorpatterns having substantially parallel legs throughout the operatingrange of stretch are also within the scope of this invention.

It can be appreciated from subsequent FIGS. 4A-C and FIGS. 5A-B that thesubstantially-parallel leg portions of the unit wave comprise asubstantially fraction of the amplitude of the unit wave. Preferably,the leg potions comprise at 0.3 or more of the amplitude, preferably 0.5or more of the amplitude, and more preferably 0.7 or more of theamplitude.

FIGS. 4A-C illustrate an actual implementation of a preferred IP sensorof this invention at three degrees of stretch. Wires 61 and 63 are IPsensor conductors, and have a preferred pattern including U-like unitwaves with substantially parallel legs at an F of approximately 6/in.Accessory conductors 65 a, 65 b, 67 a and 67 b are not IP sensorconductors, and have a sinusoidal pattern, which is not a part of the IPsensor conductor patterns of this invention, at an F of approximately4/in. They are subsequently described. The supporting elastic is acrocheted band with elastic warp filaments and on-elastic weftfilaments, and the conductors were attached to this elastic band duringcrocheting. Accordingly, this implementation was constrained by thecapabilities of readily available crocheting machines.

In FIG. 4A, the IP sensor is substantially not stretched. FIG. 4B is atthe lower end of the normal operating range of stretch, and FIG. 4A isat the upper end of the normal operating range. Examination of FIGS. 4Band 4C reveals that across the normal operating range of stretch thelegs of the U-shaped unit waves remain substantially parallel.Equivalently stated, the distances between the legs is substantiallyconstant from near the crest to near the base of the unit wave.Examination of FIG. 4A reveals that even in a substantially unstretchedstate, the legs of the unit waves remain substantially parallel.Further, these figures illustrate the considerably difference inbehavior between the IP conductors and the accessory conductors duringstretch. Examining conductors 65 a, 65 b, 67 a and 67 b in FIG. 4A ascompared to FIG. 4B and as compared to FIG. 4C reveals that the legs oftheir sinusoidal unit waves diverge considerably during stretch, orequivalently, the distance between the legs near the base of the unitwave increases by a considerably greater amount that the distance nearthe unit wave's crest.

FIG. 5A is a stylized and exaggerated, but more quantitative,illustration how one embodiment of more square-like unit waves respondsto stretch within an operational range. Pattern 71 represents an averageoperational level of stretch at which the unit wave has amplitude A andwavelength Λ. Since the largely linear bridging or cap portions 73 aregenerally more flexible than extensible, stretching an contracting isprimarily accommodated by a moving apart or a moving together,respectively, of legs 75 and 77. Preferably, an average operationallevel of stretch, the sensor is designed so that at mid-range stretchthe legs of the unit wave are substantially parallel as are legs 75 and77. Then, when largely unstretched, the legs will slightly converge aspattern 79 (depicting an exaggerated convergence), while at maximumstretch, the legs will slightly diverge as pattern 81 illustrates(depicting an exaggerated convergence). It can be readily appreciatedhow such a design provides for pattern 71 with legs that aresubstantially parallel over most of the operational range of stretch.

In more detail, the legs of largely unstretched pattern 79 converge atapproximately angle ΔΘ, and the legs of largely stretched pattern 81diverge at approximate angle ΔΘ. Preferably, ΔΘ′ approximately equalsΔΘ″, and this angle ΔΘ is given approximately by the following relation(in degrees): ΔΘ=±28*(relative stretch Δs/s in in/in)/(frequency Fin/in)*(amplitude A in in). Accordingly, where the relative stretch is10% or less, the frequency is 5.5/in or greater and the amplitude is0.35 in or greater, ΔΘ is approximately ±1.5°. Less preferably, pattern71 represents a largely unstretched state and ΔΘ is then approximately−0°+3°, or pattern 71 represents a largely stretched state and ΔΘ isthen approximately −3°+0° Note that the term “approximately parallel” isused with such a meaning, that is within approximately ±2° of beingparallel across the operating range of stretch. The term “substantiallyparallel” is taken to mean parallel within manufacturing tolerances.

Therefore, generally preferably unit wave patterns have legs withinapproximately 3° of being parallel throughout an operating range ofstretch. The term “substantially parallel throughout an operating rangeof stretch” is used with the meaning herein. It is more preferable to bedeviate less from parallelism, e.g., approximately 1-2°, and lesspreferably to deviate more, e.g., approximately 4-5°. A variation ofapproximately 5° is an upper acceptable limit, while a deviation ofapproximately ±10° or greater is to be avoided.

FIG. 5B schematically illustrates an alternative manner in which an IPconductor 87 can be attached to supporting elastic 85. Here, theconductor has unit waves that a transverse to the long axis of theelastic extending through the body of the elastic. It is preferred thatin this attachment also the unit waves have the described preferredconfiguration. Here, square-like unit waves are illustrated having, anamplitude of A and a wavelength of Λ. The values of A and Λ arepreferably scaled to achieve and amplitude-wavelength ratio ofapproximately 2 of, greater.

Wire (or other types of conductors) preferred for IP sensor conductorbalances wire gauge (smaller diameter is mechanically moreadvantageous), resistance (lower is more advantageous), and physicalflexibility (greater is more advantageous). Generally, wire with thefinest possible gauge consistent with reasonable resistance ispreferred. IT has been found that 27 or 29 AWG or higher wire with aresistance of 0.08 Ω/ft or less. Such wire is usually copper or silvercoated copper within cost constraints. If insulated, insulation shouldhave a low dielectric constant, such as expandedpoly-tetrafluoro-ethylene. Preferred wire is also as flexible (alsoreferred to herein as “limpness”) as possible to permit proper stretchand relaxation. For example, an adequately limp wire will droop over theedge of an object under its own weight. Typically, high-strand wire,approximately 51/46 of better, has been found adequate.

Further aspects of IP sensor design include external connection. Bothends of an IP sensor conductor must be attached to sensor electronics,and such connection can be a point of failure since connections of alltypes, including joints, plugs and the like are known to fail morefrequently than many other types of electrical components. This can be aparticular problem for IP sensors because the elastic substrate, incontrast to metal or plastic bases, can easily tear. IP sensors aretherefore preferably designed and constructed to have permanentlyattached external connections to the sensor conductor made at only onepoint along the sensor.

A preferred connection between sensor conductors and external wires hasbeen found suitable in many sensor embodiments, especially thosedirected to ambulatory physiological monitoring. An external wire issoldered (low temperature solder) to the sensor conductor and a sleeveis crimped about the joint. This contact provides good electricalcontact along with sufficient physical stability.

Further, to monitor many body parts, and especially for monitoring thethorax and abdomen, it is advantageous for an IP sensor and/orsupporting garment to openable and closeable, e.g., along, a midline, ofthe sensor or garment, in order that a monitored wearer can easily donthe sensor or garment. Such sensors and garments are illustrates inFIGS. 8, 9, and 10. A sensor or garment is usually provided withzippers, Velcro strips, clasps, or the like, so that it can be openedand closed, and these devices will necessarily interrupt the path of anIP sensor conductor crossing the midline. Such interruptions mayrequire, in the absence of careful configuration, additional externalcontacts.

In a preferred configuration to minimize external contacts, sensorconductors are arranged in loops with a long longitudinal axis and anshort transverse axis. The sensor conductors at one longitudinal end ofthe loop are bridged (or jumpered) together; the conductors at the otherlongitudinal loop end are available for external connection. The loop isthen arranged around a monitored body part with the garment or sensormidline passing between opposite ends of the loop without problem.Preferred sensor conductor arrangements act as relative length sensorseven when arranged in a loop having adjacent arms.

FIG. 6A illustrates an exemplary such preferred configuration. IP sensor101 having two IP conductors 103 and 105 configured with preferred unitwaves. The two conductors are bridged at 107 to form a single loop.External connections to the free ends of the loop are limited to region109. This sensor can then be arranged about a body part so that thesensor or garment midline, or closure axes, passes between the ends ofthe loop at 107 and 109. Since no external leads need cross theseparation axis, this configuration requires no plugs for attachment andremoval of any external bridging leads. FIGS. 6A-D are further describedin the following.

FIGS. 6B-C illustrate additional exemplary configuration in which sensorconductors are arranged in a loop in order to minimize externalcontacts. FIG. 6B illustrates IP sensor 111 having four IP conductorsconfigured into a single folded loop. The two outer pairs of conductorsare bridged 113 at one end, while the inner pair of conductors isbridged 115 at the opposite end. External connect ions are made to thetwo outer conductors at 117. Any even number of sensor conductors can besimilarly configured. A functional alternative to four conductor sensor111 is a two conductor sensor similar to 101 but having unit waves withtwice the amplitude of the unit waves of sensor 111.

FIG. 6C illustrates is sensor 119 which is similar to sensor 111 butinstead bridged at 121. External corrections are made at 123. Conductors125 and 127 are externally unattached and not functional. This type ofsensor is advantageous when it is needed to monitor only limited portionof a body part, i.e., the length between 121 and 123, without disturbingthe remaining two lengths of conductors.

In some cases, an IP sensor, perhaps attached to or part of a garment,can be placed about a monitored body part by slipping the garment ontothe part without need to opening or closing Here the a single sensorconductor can encircle the body part with external contacts made in alimited region. Bridging is not needed. Alternatively, one of theconfigurations illustrated in FIGS. 6A-D with bridged conductors can beused.

Multifunctional IP Sensors—Accessory Conductors

In a further aspect of this invention, the supporting elastic of an IPsensor supports, in addition to the IP sensor conductors, additionalconductive elements (referred to herein as “accessory conductors”),additional sensors, and the like, thereby forming a multifunctional IPsensor. Accessory conductors (also referred to herein as “channels”)generally arranged in a linear fashion along a longitudinal dimension.FIG. 7A illustrates and IP sensor (similar but not identical to the IPsensors in FIGS. 4A-C) having two IP sensor conductors 145 along themidline of the supporting elastic, two accessory conductors 141 adjacentto the top edge of the supporting elastic, and two additional accessoryconductors 143 adjacent to the bottom edge of the supporting elastic.The IP conductors and the accessory have different longitudinalwavelengths. Although their amplitudes here are approximately equal, inother embodiments their amplitudes can differ.

Types of linear conductive elements are suitable for this invention havesufficiently small size and sufficient flexibility to be incorporatedinto the supporting elastic, particularly elastic fabric, during itsproduction process. Alternatively, accessory conductors (and IP sensorconductors) can be operably affixed to the supporting elastic in apost-production step. Conductive elements are incorporated or affixed tothe supporting elastic in a manner so as not to impede the fabric'selasticity and/or stretch ability. Preferred conductive elements includebare or coated wire, shielded coated wire, coaxially shielded wire, andthe like. Other types of possible conductive elements include flexiblewires (with higher wire gauges) of virtually all types, includingtelephone-type wire and cables, twisted pairs, category 5 gradeconnections generally, ribbon wire, and the like.

IP sensor conductors are necessarily unshielded, typically of smallerwire sizes, and, as described, arranged at the preferred wavelengths andamplitudes and in the preferred patterns. Unshielded wire can also beused for interconnecting electronic components, for example, forinterconnecting a sensor placed on or contiguous to the supportingelastic of an IP sensor with its elsewhere-located processingelectronics. However, shielded wire or coax can be preferred to avoidelectrical cross-talk and interference dues to adjacent IP sensors andother sources of electrical interference.

Preferred shielded wires, shielded wires, coax, and other conductiveelements have an outside diameter (OD) of 1.0 mm or less, or 0.9 mm orless, or 0.8 mm or less, or 0.7 mm or less, or 0.6 mm or less, or 0.5 mmor less, and have a highly conductive element which is highlyconductive, for example, having a resistance less than 0.1 ohm/foot.Copper is a preferred conductor; silver coated copper can be used ifnecessary. Preferred coats and insulations generally have low dielectricconstant large breakdown voltage and include fluorinated ethylenepolymers (FEP), silicone polymers, and the like. In particular,preferred wires include 29 gauge with high-count bare copper strands(51/46), with 0.083 ohm/foot, with 0.5 mm OD, and with FEP of siliconecoating. Preferred coax has a 50 ohm impedance and a 0.81 mm OD. Smallcoax, also known as micro-coax, is available from, for example,Micro-Coax, Inc. (Pottstown, Pa.; http://www.micro-coax.com/(lastvisited Sep. 20, 2004)).

In order to accommodate the limited longitudinal elasticity of mostconductive elements, preferred embodiments incorporate sufficient excesswire length so that, at the maximum stretch of the supporting elastic,the conductive elements will be under only minimal or no tension.Preferably, in an unstretched length S of supporting elastic a length ofa conductive element W>S is incorporated or affixed that is equal to orgreater than the maximally stretched length of the elastic, S′. Further,the conductive element is incorporated or affixed such as to permit thesupporting elastic and the conductive element to move relatively duringstretch. Thus, the conductive element will not be tensioned at any levelof stretch throughout the maximal range of stretch. The length ofconductive element per length of elastic is specified herein by theW−/−S ratio (greater than 1).

Conductive elements are incorporated or affixed to supporting elastic ina generally linear manner along the stretch axis but with repeatedtransverse (to the stretch axis) deviations so that W−S additional wirecan be present into an elastic of length S. The transverse deviationsare preferably in the plane of the elastic but can also be at an angleto this plane as in FIG. 5B, so that the conductive element extends bothbetween the elastic surfaces. Although many forms of repeated, limitedtransverse deviations also possible, a preferred arrangement is in aprescribed pattern of limited curvature hi order to avoid kinks andbreaks of the accessory conductors (excepting IP sensor conductors),especially of shielded wire, coax, and multi-wire cables.

FIG. 7B illustrates a detail of two accessory conductors 149 affixed toa supporting elastic fabric 151. These conductors have a preferredpattern with a smoothly varying and limited curvature, hereapproximating a sinusoidal pattern. It can be appreciated how transversedeviations, determined by the wavelength, Λ, and amplitude, A, of thesinusoidal pattern, provide sufficient excess conductor length forelastic 151 to stretch without tensioning conductors 149. Conductors 149are retained by the warp filaments in a manner permitting the sinusoidalpattern to readily flatten and lengthen, i.e., , increased Λ anddecreased A.

Preferably, the excess conductor length W−/−S

The W−/−S ratio is readily determined from the following relation:

W−/−S=(1.2/Λ)*SQRT(2*(A**2)+Λ**2)

For example, for an accessory conductor, if Λ=0.33 in. (frequency=3/in.)and A=0.22 in., then W−/−S=2.4. And for an IP sensor conductor, if Λ=0.2in. (frequency=5/in.) and A=0.32 in., then W:F=3.8. Preferably, theexcess conductor length, the W−/−S ratio, is adequate to preventtensioning the conductor but not excessive in order to minimize weight,improve elasticity, and reduce cost (micro-coax currently beingrelatively expensive). A range of the W−/−S ratio from approximately 2to approximately 3 has been found suitable.

In preferred multifunctional sensors, unshielded IP sensor conductorsand accessory conductors each have each particular preferredcharacteristics, e.g., type of conductor, amplitude, and frequency. IPsensor conductors preferably have, as described above, an F (frequency1/Λ) of approximately 5.0 or greater, to approximately 5.5 or greater,and approximately 6.0 or greater. Their amplitude, A, should usually beas large and an elastic can accommodate; one conductor with an A orapproximately 0.6-1.0 in. or greater, or two conductors each with an Aof approximately 0.30-0.40 inch or greater has been found suitable.Accordingly, IP conductors have larger W:F ratios

Accessory conductors, e.g., shielded wire, or coax, or other types ofwires, preferably have W:F: ratios from approximately 2 to approximately3. A and F can be chosen accordingly. For example, F can beapproximately 2.5-3.5/in., and A can be approximately 0.3 inch toapproximately 0.3 inch.

The supporting elastic should be wide enough to accommodate allconductors, or approximately the sum of the amplitudes of all supportedconductors, within limits of subject comfort and acceptability.Multifunctional sensor can have from 1, to 2, to 4 or more IP sensorconductors with no accessory conductors or with 1, to 2, to 4, to 6, andto 8 or more.

Multifunctional IP Sensors—Additional Elements

IP sensors having accessory conductors can perform additional non-IPfunctions (referred to herein as “multifunctional IP sensors” or as“multifunctional sensors”). For example, the accessory conductors canelectrically link additional sensors of various types to externalconnections and thereby to their processing devices. Preferably,additional sensor are adjacent to or in contact with the sensor or canbe mounted on the supporting elastic of the sensor. A multifunctional IPsensor can have various physical arrangements configurations, e.g., froma band-like configuration extended along a single direction toconfigurations of approximately equal dimensions in all directions.Further, a multifunctional IP sensor can be configured as a garment tobe worn by a monitored subject or can be mounted on supporting apparel.IP sensors can support 2, or 4, or 6, or more IP sensor conductors and2, or 4, or 6, or more accessory conductors.

In the following, exemplary band-like multifunctional IP sensors havingselected additional functions are illustrated and described. However,the described sensors are not limiting, and it be apparent to one ofskill in the art from the following how multifunctional sensors of otherconfigurations and functions can be constructed.

FIG. 8A-C schematically illustrate exemplary band-like multifunctionalIP sensors. The sensors themselves can serve as apparel or be mounted onsupporting apparel. For clarity, these figures do not provide detailsalready described and illustrated. Importantly, both IP sensorconductors and accessory conductors are generally illustrated usually assimple lines without details. Actual implementations of these conductorswill, however, have the characteristics already described. Also, detailsincidental to this invention are not shown. For example, snaps, buckles,electrical connectors, and the like, are illustrated only in outline assuch elements can be supplied by one of skill in the art. Similarly,embodiments may require conductive elements for separate signal andground connections, which also can be supplied by one of skill in theart and are not separately illustrated.

FIG. 8A illustrates simplified IP multifunctional sensor 171 having IPsensor conductors configured similarly to sensor 111 (FIG. 6A). Sensor171 also supports accessory conductor 173 which connects externallythrough connector 175 to additional sensor 177, e.g., an antenna loop,which is placed adjacent to sensor 171. The accessory conductor alsoconnects externally at connector 179, and electrically links the antennato processing circuitry. The accessory conductor is illustrated ashaving a sinuous waveform with the above-described preferredcharacteristics.

FIG. 8B illustrates a IP multifunctional sensor 181 having twoconductive elements and performing three sensor functions. Sensor 181 isfor into a loop suitable for placing about, for example, the torso of ansubject, and can be either incorporated as part of a, e.g., shirt-likeor vest-like physiological monitoring garment perhaps includingadditional sensors, or it can be configured as a band-like garment withonly such additional coverings as are necessary for comfort,convenience, and protection. The sensor can be provided with clasps,snaps, zippers, and the like, for their longitudinal connection acrossmidline region 187. As illustrated, electrical connection to thesensor's conductive elements are made at left and right ends 183 of thesensor in midline region 187. In another embodiment, the sensor may becontinuous and longitudinal connectors are can be dispensed with whileelectrical connection can be made to the conductive elements by thepreferred connectors or other means at the sensor's outer face.

Conductive element 189 runs from one end of the sensor to the other endaround the sensor without interruption and can server as an IP sensor.Although a loop configuration with external connection at only one endis generally preferred, the illustrated configuration is suitableespecially when the sensor is continuous. Conductive element 189 isillustrated as linked to external IP sensor electronics 191.

Conductive elements 193L and 193R (collectively, 193) link to sensors195 and 197. Left half 193L carries signals from sensor 195 to the leftedge of the sensor, and right half 193R carries signals from sensor 197to the right sensor edge. The portion between sensors 195 and 197 iselectrically interrupted if necessary so that the signals from bothsensor can be externally distinguished. Sensor electronics 199processes, signals from sensor 195 and links to 193L. Similarly, sensorelectronics 201 processes signals from sensor 197 and links to element193R. Thereby, the single conductive element 193 (193L and 193R) canprovide external connections for two separate sensors. In preferredembodiments, sensor electronics 191, 199 and 201 are packaged into asingle physical module.

Sensors 195 and 197 can include various physiological sensors including,for example, microphones, thermometers, ECG electrodes, accelerometers,and the like, also sensors for electroencephalograms, electrooculograms,electromyograms, and the like, as well as other non-physiologicalsensors. They can be physically incorporated into or supported by thesupporting elastic of sensor 181 or can be carried by associatedapparel. Elements 195 and 197 can also be other components that can besized and configured to be compatible with sensor 181, e.g., electronicsmodules perhaps for one or more of sensors 195, 197, and IP conductor189.

FIG. 8C schematically illustrates another band-like multifunctional IPsensor 205 having six or more conductive elements and intended toencircling the thorax of a monitored subject. Although not illustratedin this figure for clarity, it should be understood that conductiveelements extend entirely around the sensor but with electricalinterruptions as necessary, and also have the preferred andpreviously-described patterns. In particular, IP sensor conductors havethe preferred patterns described above (regardless of the illustrationhere).

Connectors 207 a and 207 b (collectively, 207) mechanically link bothedges of the sensor and provide electrical connections betweenconductive elements on either side of the sensor and/or to externalunits. If the sensor is continuous, such connectors are not needed.Connections between conductive elements and external sensors can be madeas known in the art by plugs, or by retainers holding the conductiveelement in contact with a conductive pad on the sensor, or by solder, orthe like. Connections between conductive elements and sensors arepreferably soldered joints covered by a sleeve as described.

In a preferred embodiment, sensor 205 includes an two IP sensorconductors 221 and 223 which are bridged into a single electrical loopat 225 and linked externally at single connector 207 a. The sensor alsosupports three electrocardiogram (ECG) sensors 209, 211 and 213 on thesensor's inner side to be electrical contact with a subject's skin anddistributed around the anterior thorax. These ECG electrodes are linkedto connectors 207 (and on to external units) by shielded conductiveelements 215, 217 and 219, respectively, to reduce electrical noise inthe ECG signal.

Sensor 231, linked by shielded or unshielded conductive element 233,senses, in one embodiment, subject surface temperature. Sensor 227linked by shielded conductive element 229 is, in one embodiment, animpact microphone sensitive to sounds of potentially dangerous impactson the subject. Sensors 227 and 231; or additional sensors, canalternatively be accelerometers, and the like, or can also be electronicmodules as described.

A Preferred Supporting Elastic Material

In preferred embodiments, the supporting elastic for the IP sensors andmultifunctional IP sensors of this invention is formed into bands havinglongitudinal lengths that are considerably longer than their traversewidth. For example, typical band widths (transverse sizes) are between 1and 2 inches, or between 2 and 4 inches, or between 4 and 6 inches; andtypical band lengths (longitudinal sizes) are from 1 foot to severalhundred feet. Accordingly, this preferred supporting elastic is alsoreferred to herein as “bands” or “elastic bands”.

For an elastic band stretchable in the longitudinal direction, thefilaments comprising the warp are elastomeric. Spandex® or Lycra® haveproven most suitable in the present invention. These manmade strandshave superior elasticity and have been found to be less abrasive andless irritating to bare skin than natural strands. However, for thoseapplications in which direct contact between the skin and the fabric 10,100 is not contemplated, extruded natural latex strands will providesatisfactory elasticity.

A variety of fill, or weft, yarns may be used to complete the formationof the supporting elastic material. While single ply, 150 denierpolyester is quite suitable, other suitable yarns including 2 ply, 70denier nylon; 2 ply, 100 denier nylon; and, 2 ply, 150 denier polyester,have been found suitable. However, other yarns, formed of natural andman-made materials, as well as other deniers, may also be suitably used.Further, bands preferably have selvage along longitudinal edges.

The elongated band of supporting elastic material can be formed in anyof the conventional ways for forming elastic fabrics including warpknitting, weft knitting, weaving, or braiding. Warp knitting on acrochet machine is particularly suited to the present invention sincethis type of machine is easily adaptable to producing elastic fabricbands having narrow widths. One such machine is an 8-bar crochet machinemanufactured by Jacob Muller as Model RD3-8/420 (8-bar, 420 mm).

Conductive elements can be operably affixed to the supporting elastic bysewing in a separate operation subsequent to formation of the band, butit has been found most efficient and cost effective to form the entirecomposite elastic and wire fabric integrally in the same knittingoperation. When the conductive elements are affixed during elasticformation by knitting and the like, it has been found that a knittingpattern movement allowing the conductive element to remain betweenknitting needles for two consecutive stitches provides an optimalconstruction that permits the conductive elements to stretch uniformlyas supporting elastic stretches.

In forming a knitted fabric structure, the crochet machine draws eachindividual warp yarn through a guide mounted on a guide bar. Tension isapplied to stretch the warp yarns. Movements of a plurality of guidebars cause each yarn to loop around a needle. After the yarns arelooped, the needle bar on the machine is moved so as to cause loops tobe formed simultaneously at all needles, resulting in a whole knittedcourse. A yarn inlay is next drawn across the lower warp yarns. As theguide bar is displaced sideways by one or more needles, the upper andlower warp yarns change places before the next cycle produces anothercourse. The displacing of the guide bar determines the structure of thefabric.

For an IP sensor with, e.g., three conductive wires having the samewavelengths, amplitudes, and unit waveforms, the machine is setup withthe number of warp yarns (e.g., approximately 17 or more Lycra® warpyarns) and at least one nylon or polyester weft inlay yarn. Odd numberedwarp yarns are on one beam or bar, while even numbered yarns are onanother beam or bar. In addition to this, another beam or bar (referredto as the “control bar”) of the three conductive wires is setup and fedthrough yarn guides that are directed by this control bar.

This control bar moves the three guides back and forth across the fabricin a repeating sequence positions (positions being defined by adjacentwarp yarns) as the fabric is being formed, preferably remaining in eachposition of the sequence for approximately two stitches. This positionsequence of the control bar determines the wavelength, amplitude, andunit waveform in which the conductive wires are affixed. Two or moreconductive wires can be independently affixed with separate selectedwavelengths, amplitudes, and unit waveforms (see, e.g., FIG. 7A) using asetup with two or more beams or bars that are separately controlled inseparate repeating position sequences.

For example, for an IP sensor similar to that illustrated in FIG. 7A,the warp and weft filaments are woven in a conventional manner using upto four controlling bars. The control bars for the IP sensor conductors(145 in FIG. 7A) are programmed to have a position sequence of0-0-0-4-4-4-0-0-0-4-4-4, and the control bars for the accessoryconductors (141 and 143 in FIG. 7A) are programmed to have a positionsequence of 0-0-1-1-2-2-3-3-2-2-1-1. An alternative position sequencefor the accessory-conductor control bar is0-0-1-1-2-2-3-3-4-4-3-3-2-2-1-1, which affixes an accessory conductor toan approximately 1.5 in. wide band with approximately 15 or more warethreads with a sinusoidal pattern having an amplitude and, wavelength ofapproximately 0.4 in. Alternatively, the elastic can be woven so thatwarp and weft filaments are at an approximately 45° angle to each other,to the conductors, and to the longitudinal edges of the elastic.

Other machine setup parameters can be routinely selected. In particular,the elastic is preferably formed under an tension approximate equal tothe upper limit of the operational range of stretch. A stretch ofapproximately 80% has been found suitable for physiological monitoringembodiments. It is also preferable to put more tension on the warpfilaments that retain the conductors.

In detail, setup instructions for an eight bar crocheting machine tomake the IP sensor of FIG. 7A include the following:

# BAR (ends) TYPE SEQUENCE 1 4 1/150 SD 1 - 31 - 1 - 31 - 1 - 31 - 1 -31 - 1 - 31 - 1 - 31 2 29 1120 clear 1 - 2 - 2 - 1 - 2 - 1 - 2 - 1 - 2 -1 - 2 3 4 2 Rip 0 - 0 - 0 - 4 - 4 - 4 - 0 - 0 - 0 - 4 - 4 - 4 5 4Coaxial 0 - 0 - 1 - 1 - 2 - 2 - 3 - 3 - 2 - 2 - 1 - 1 6 4 1/150 SD 31 -1 - 31 - 1 - 31 - 1 - 31 - 1 - 31 - 1 - 31 - 1 7 8 Warps 29 1/150 SD

The following instruction supplement the above table:needles—width—31−2; stretch at knitter—80+/−10%; stretch after 2hours—80+/−10%; stretch after, calendar—n/c; front picks—18; back picksat knitter—30+/−1; back picks after 2 hours—30+/−1; back picks aftercalendar—n/c

Those skilled in the art will appreciate that there are other ways toform constructions teat will function as desired. For example, an IPsensor can be formed by braiding in known manners. For another example,an IP sensor can be formed in a non-woven embodiment. At least oneconductive wire, shaped in a sinusoidal arrangement is placed in a longnarrow mold. Manufactured filaments; e.g., polyester, nylon, etc., areextruded and crisscrossed over at least one side of the shaped wire toform a web or mesh-like overlay. Finally, a film of elastomeric fiber isextruded to encapsulate one or both surfaces of the wire and web layers.When cooled and dried, this structure will stretch and contract todeliver a satisfactory, reliable output signal.

The inventive principles described herein can also be applied to producethis composite fabric in other shapes, such as sheets or tubes. Forexample, this present invention also includes embodiments in which twoor more elongated supporting elastic bands are joined into a singlesupporting elastic band with multiple layers, or in which a single widerelastic band is folded longitudinally and joined to form a singleelastic band with multiple layers. Two of more elastic bands each with asingle wire type in a pattern preferred to that wire type can be joinedinto a multiple layer supporting elastic band. One band of a joined pairof elastic bands can have unshielded wires at 5-6/in. and the secondelastic band can have coax at 2-3/in. Another multiple layer embodimentcan circumvent conductive element-number limitations of elastic bandswith useful widths. A single elastic band with a width of 3.5-4.5 inchescan woven to accommodate up to 4-6 unshielded and up to 4-6 coaxconductive elements, and then folded longitudinally one or more timesand joined along free edges. A multifunctional IP sensor so constructedcan have up to 8, or 10, or 12 conductive elements in a net width ofapproximately 1.75 to 2.25 includes Elastic band edges may be joined asis known in the art by stitching, by thermal bonding, by ultrasoundbonding, and the like. Also two or more elastic bands or an elastic bandfolded one or more times can also simply enclosed in a thin fabricsleeve.

Regional Physiological Monitoring Apparel

IP sensors and multifunctional IP sensors of this invention can bearranged over portions or regions of a monitored subject so thatmovement of the underlying region are monitored (referred to herein as“regional physiological monitors” or “regional monitors”). As described,signals from IP sensor conductors are primarily responsive to the totallength of the sensor. Therefore, signals from regional physiologicalmonitors will be primarily sensitive to areas, circumferences,diameters, and similar measures depending on how they are arranged andthe geometric constraints of their arrangement. For example, a regionalsensor over an anterior portion of the thorax will sense expansion andcontraction only of that underlying anterior portion, while a regionalsensor encircling the thorax will sense expansion and contraction of thewhole thorax.

Regional physiological monitors have many applications. For example,regional monitors over the left and/or right sides or the thorax and/orabdomen are most responsive to respiratory motions in the left and/orright lung, respectively, and provide indications of differential lungfunction. See, e.g., U.S. Pat. No. 5,159,935 issued Nov. 3, 1992 (whichis incorporated herein by reference in its entirety for all purposes).Monitoring of differential lung function has numerous uses in assessingunilateral parenchymal disease, plural effusion or disease, pulmonaryembolus, guarding due to pneumonia or other disease, and the like.Moreover, using such sensors, differential lung function can bemonitored in ambulatory subjects.

FIGS. 9A-C illustrate an exemplary embodiment of a regionalphysiological monitoring apparel. As in FIG. 8B-C, for clarity thesefigures, and subsequent FIG. 10A-B, do not provide details alreadydescribed and illustrated. Importantly, both IP sensor conductors andaccessory conductors are generally illustrated usually as simple lineswithout details. Actual implementations of these conductors will,however, have the characteristics already described.

Specifically, FIGS. 9A-C illustrate a garment including only IP sensorsupporting elastic band 251 along with coverings useful for comfort anddurability. FIG. 9A is an anterior illustration; FIG. 9B at lateralillustration; and FIG. 9C a posterior view. Identical reference numbersindicate the same structure on these three figures. This garment may becontinuous for slipping over the head, or may have a zipper, Velcrostrip, and the like along midline 253 so that it can be opened andclosed. This garment and IP sensor includes three IP conductor loops,loops 255, 261, and 267.

Loop 255 largely encircles the rib cage and provides signals reflectingrib cage expansion and contraction, i.e., reflecting respiration. Itincludes two IP sensor conductors, bridge 259 between the conductors,and connectors 257 linking the conductors to external leads. Loop 261overlays a left lateral portion of the rib cage and provides signalsreflective of the expansion and contraction of the underlying regions ofthe left lung. This loop also includes two IP sensor conductors, bridge265 between the conductors, and connectors 263 linking the conductors toexternal leads. Finally, loop 267 overlays a right lateral portion ofthe rib cage and provides signals reflective of the expansion andcontraction of the underlying regions of the right lung. This loop alsoincludes two IP sensor conductors, bridge 271 between the conductors,and connectors 269 linking the conductors to external leads. Asdescribed in U.S. Pat. No. 5,159,935, Signals from IP sensors 261 and267 can be calibrated to yield indicia of left and right lungrespiratory volumes, respectively, and the temporal variation of theserespiratory volumes. See, e.g., U.S. Pat. No. 5,159,935.

FIGS. 10A (anterior view) and 10B (posterior view) illustrate anotherexemplary embodiment of a regional physiological monitoring apparel.Garment 291 is in the form of a sleeveless shirt with midline closure293, e.g., zipper, Velcro, or the like, for opening and closing thegarment. If the garment is configured to be a pull-over, midline closure293 can be dispensed with. The garment supports six IP sensors—295, 297,299, 301, 303 and 305—acting as regional monitors. Garment 291 issufficiently elastic so that the expansions and contractions ofunderlying torso regions is reliably transmitted to the IP sensors. Forsimplicity, all the IP sensors are illustrated as including to sensorconductors which a bridged at one end to form an electrical loop.External contacts, schematically represented with the symbol “◯” areprovided and the other end of the conductors.

Comparing the signals from the supported IP sensors providesphysiological monitoring information on total and right-left differences(“differential”) lung and heart function. IP sensor 295 and 297 areprimarily sensitive to regional expansions and contractions of the leftportions of the rig cage and abdomen. As described, these signals can becombined into a reliable indication of left lung functioning. IP sensor299 and 301 are primarily sensitive to regional expansions andcontractions of the right portions of the rig cage and abdomen. Asdescribed, these signals can be combined into a reliable indication ofright lung functioning. Differences between right and let lung functioncan indicate pathological conditions as described. The sum of the rightand left lung function provides a reliable indication of overallrespiratory function, including respiratory volumes and respiratoryrates. Additionally, comparing signals from abdominal sensors 397 and301 can indicate differential abdominal motions that can occur inabdominal disease, where it is know as “guarding”, and other similarinformation.

IP sensors 305 and 303 are primarily sensitive to regional expansionsand contractions of the left and right portions, respectively, of theanterior thorax. The sum of signals from both these sensors providesadditional information on respiratory function and can includecomponents reflective of cardiac pulsations. The difference of signalsfrom these sensors provides additional information on differentialrespiratory function and can include components more reflective ofcardiac pulsations, since these pulsations will primarily appear insignals from IP sensor 303 overlying the heart in comparison to signalfrom IP sensor 305.

The invention described and claimed herein is not to be limited in scopeby the preferred embodiments herein disclosed, since these embodimentsare intended as illustrations of several aspects of the invention. Anyequivalent embodiments are intended to be within the scope of thisinvention. Indeed, various modifications of the invention in addition tothose shown and described herein will become apparent to those skilledin the art from the foregoing description. Such modifications are alsointended to fall within the scope of the appended claims.

A number of references are cited herein, the entire disclosures of whichare incorporated herein, in their entirety, by reference for allpurposes. Further, none of these references, regardless of howcharacterized above, is admitted as prior to the invention of thesubject matter claimed herein.

What is claimed is:
 1. A method for measuring physiological data of auser, comprising: providing two stretchable sensor conductors onto abody part of a user, wherein: each stretchable sensor conductor isconfigured to expand and contract with the movement of the body part;each stretchable sensor conductor includes an external contact point,the stretchable sensor conductors are connected through a bridgingconnection at a first end of the stretchable sensor conductors, and theexternal contact points are located at a second end of the stretchablesensor conductors; and measuring an electrical characteristic of thestretchable sensor conductors which changes with expansion andcontraction of the body part, to obtain physiological data.
 2. Themethod of claim 1, further comprising: connecting the sensor conductorsto an impedance measuring circuit; and determining the impedance ofsignals received from the stretchable sensor conductors.
 3. The methodof claim 2, wherein the impedance measuring circuit includes anoscillator.
 4. The method of claim 3, further comprising: matchingresponse characteristics of the stretchable sensor conductors withresponse characteristics of an oscillator circuit across the operatingfrequency range of the oscillator.
 5. The method of claim 4, furthercomprising: determining a frequency of an oscillator output signal; anddetecting the frequency of the oscillator output signal with a frequencydetector.
 6. The method of claim 1, wherein the stretchable sensorconductors operate in a frequency range of 150 kHz to 600 kHz.
 7. Themethod of claim 1, wherein the stretchable sensor conductors operate ina frequency range of 300 kHz to 310 kHz.
 8. The method of claim 1,further comprising: providing the stretchable sensor conductors around arib cage of the user, wherein the electrical characteristic reflects ribcage expansion and contraction,
 9. The method of claim 8, wherein thesignals are calibrated to indicate the respiratory volume of the lungs.10. The method of claim 1, wherein the stretchable sensor conductors areincorporated in a stretchable garment.